Aspectj Cookbook

2017-07-07 02:10:07

Recipe 2.7. Compiling an AspectJ Project Using Eclipse

Problem

You want to compile your AspectJ project using Eclipse.

Not Using Eclipse or Ant?

If you are not going to use Eclipse or the Ant tool when writing your aspect-oriented software with AspectJ, then it is worth skipping forward to the next chapter to start looking at the common approaches to deploying your AspectJ applications.

Solution

Download and install the AspectJ Development Tools (AJDT) plug-in into Eclipse.

Discussion

AspectJ is run under the same open source collective as the Eclipse project and provides the most advanced AspectJ plug-in for an IDE. The AspectJ Eclipse plug-in can be downloaded by following the instructions available at http://www.eclipse.org/ajdt.

It's a good rule of thumb to download the latest version of AspectJ, the corresponding latest version of the AJDT, and then download the supported version of Eclipse just in case the Eclipse tool is a step or so ahead of the AspectJ development. If you are ever confused by the options available, there is a compatibility table available on the AJDT downloads page to point you in the right direction.

To check that the plug-in has been correctly installed, click on File New Project... on the Eclipse menu bar. When the New Project dialog appears, the AspectJ project option should be available, as shown in Figure 2-1.

Figure 2-1. Creating a new AspectJ project

By default, early milestone builds of Eclipse 3 hid all additional wizards. To see the New AspectJ Project option, you may have to select the Show All Wizards checkbox.

Highlighting the AspectJ Project option, click on Next in the New Project dialog and complete the next few steps to set up the new AspectJ project.

Once the project wizard has completed, you may be asked to switch to the Java perspective. You may also be asked for some AJDT preferences if this is the very first time that you have used the wizard. It's a good idea to switch to the Java Perspective and accept the default values for the project preferences. Once Eclipse has switched to the Java perspective, your project should look like Figure 2-2.

Figure 2-2. AspectJ project sources and jars within the Eclipse Java perspective

By default from AJDT 1.1.7 onwards, an AspectJ project will incrementally compile all changes to your aspects and Java classes. This option can be turned off in the Eclipse AspectJ project configuration if the build performance becomes too intrusive.

Your new AspectJ application should automatically compile with the creation of the new project. If you are at all worried that this hasn't happened, click on the Build AspectJ Project button shown in Figure 2-3. This will force a rebuild of the project just to be sure.

Figure 2-3. Use the Build AspectJ Project button to check that your project has compiled correctly

Your application is now compiled and ready for running, but before you run it, it is interesting to note the enhancements that the AJDT brings to the Java perspective. Perhaps the most obvious enhancement is in the contents of the Outline view which will contain, when an aspect or advised class is selected, new sections indicating where advice has been applied. An example of the additional information available in the Outline view is shown in Figures Figure 2-4 and Figure 2-5.

Figure 2-4. Using the Outline View to see on which classes or aspects a specific advice is applied

Figure 2-5. Using the Outline View to see what advice is applied to a specific class

The AJDT also provides another view of your project that graphically displays an overview of how your aspects are applied to your application, The Aspect Visualization perspective can be opened by selecting Window Open Perspective Other... and then enabling the Aspect Visualization perspective. The new perspective on your project will then show a graphical depiction of how the aspects have been applied to the classes as shown in Figure 2-6.

Figure 2-6. The AJDT Aspect Visualization perspective with an example project selected

Switching back to the Java perspective, it's time to run your application. In Eclipse, it is as easy to run an AspectJ application as it is to run a traditional Java application. In the Java perspective, click on the class that contains the public static void main(String[]) method and select Run Run As Java Application from the main menu. Eclipse will then search and run the public static void main(String[]) method in the selected class producing the applications command line output to the Console view as shown in Figure 2-7.

Figure 2-7. The output on the Console view when Recipe 5.1 is run

There are enough features and enhancements supported by the AJDT to fill a chapter in its own right. Take some time to tour the different preferences and features that are available, perhaps while you work with some of the other recipes in this book, to help you get used to what features are most useful to you.